88 



Scientific Proceedings (8i). 



For details see April number, Journal American Chemical 

 Society, 191 7. 



56 (1234) 



A contribution to the metamorphosis of skin in amphibians. 

 By Edward Uhlenhuth. 



[From the Laboratories of the Rockefeller Institute for Medical 



Research,] 



Gudernatsch has shown that thyroid is able to induce meta- 

 morphosis in frog and toad larvae, if they are fed on this gland. 

 The effect was so striking that metamorphosis sometimes started 

 five days after thyroid was fed. 



From these experiments it is however not certain that thyroid 

 is the substance which under normal conditions causes meta- 

 morphosis, nor has it been proven by these experiments that an 

 agent similar to its physiological character is involved in normal 

 Amphibian metamorphosis. 



In a series of experiments it has been shown, that also under 

 normal conditions some agent must be furnished to the organs of 

 the animal in order to bring about metamorphosis of these organs. 

 It has turned out that the organs themselves are unable to produce 

 this agent and that it is the body which produces the agent, i. e., 

 some place or organ in the animal's body remote from the organs 

 examined. If this agent is prevented from reaching the organ, 

 it will not metamorphose. 



The general method of these experiments is to remove the 

 organs from the animal's body, before the body begins to produce 

 the agent and to graft it to another animal in which the agent 

 will not be produced for a long time. By means of this meta- 

 morphosis of the organ can be inhibited for as long as the new 

 host does not metamorphose; in this way metamorphosis could 

 in some cases be delayed by seven months. Until now the eyes, 

 the skin and the gills — the latter by Kornfeld — were studied in 

 this way. Today we will report mainly on experiments performed 

 on the skin of Ambly stoma punctatum. 



In order to make you familiar with the changes occurring in the 

 skin of this animal during development I will show a few pictures. 



